This invention relates to infra-red (IR) detectors. More particularly, this invention relates to uncooled thermal IR detectors utilizing ferroelectric thin films as imaging elements.
Infrared detectors include both photon and thermal detectors. Photon detectors (e.g., PtSi available from Honeywell and CdTe available from Raytheon) can offer good sensitivity, fast response times, high spatial resolution, and low cost if standard semiconductor processing technology can be used. However, these detectors are sensitive to thermal noise effects and must be cryogenically cooled. The cooling units are expensive and cumbersome, making photon detectors
Impractical for most consumer and military applications. In addition, semiconductor infrared detectors suffer from pixel-to-pixel signal variations that make signal processing necessary in order to obtain &lt;1.degree. C. resolution. The process of mathematically normalizing the signal from each pixel reduces the signal-to-noise ratio of the array.
Thermal detectors, like pyroelectric imaging elements, offer excellent performance at room temperature and do not require cooling. They are suitable for small, light-weight detection systems that are reliable and require minimal power. Until now, these detectors have been difficult and costly to fabricate. The pyroelectric imaging elements manufactured at Texas Instruments consist of a laser reticulated barium strontium titanate (BST) ceramic that has been flat-lapped to a thickness of &lt;20 .mu.m and then bump-bonded to an integrated circuit. The lapping process is wasteful and time-consuming, and the bonding process often leads to breakage of the very delicate BST ceramic. Therefore, the technical problem with these detector elements is that throughput is low and cost is high ($2500/detector array). In addition spatial resolution is limited (48 .mu.m pixel size) because of the difficult bump-bonding process.